A lithographic apparatus is a machine that applies a desired pattern onto a target area of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target area (e.g. comprising part of, one or several dies) on a substrate (e.g. a silicon wafer) that has a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target areas that are successively exposed. Known lithographic apparatus include so-called scanners, in which each target area is irradiated by scanning the pattern through the beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti parallel to this direction.
The number of substrates which may be patterned per hour by a lithographic apparatus (often referred to as throughput) is a key metric of lithographic apparatus. It is desirable to increase the throughput of a lithographic apparatus because this will increase the profitability of that lithographic apparatus.
It is desirable to provide, for example, a lithographic apparatus which operates in a manner that is not taught or suggested by the prior art, and which may allow a throughput increase to be obtained.